Heat Sealable Packaging Material with Improved Hot Tack

ABSTRACT

A packaging material includes a substrate and a heat seal layer. The heat seal layer comprises polyvinylidene chloride. The packaging material includes at least about 8 wt % moisture for increasing the hot tack of a seal formed between a first portion of the heat seal layer and a second portion of the heat seal layer relative to a packaging material with less than about 8 wt % moisture. If desired, the packaging material including the at least about 8 wt % moisture may be formed into a roll.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/300,134, filed Feb. 1, 2010, which is incorporated by reference inits entirety.

BACKGROUND

Form and fill type packaging machines are commonly used for a variety ofpackaging applications. In such machines, a packaging material istypically unwound from a roll, formed into a tube around a mandrel, andthe free edges are sealed together (e.g., to form a fin seal). Thebottom end of the tube is then sealed together to form an end seal,often using a pair of heated jaws or clamps. As the seal is beingformed, the items to be packaged are inserted (often dropped) into thepackage. As a result, the newly formed heat seal needs to havesufficient “hot tack” or “hot tack strength” to support the weight ofthe package contents. Thus, there remains a need for packaging materialsthat provide sufficient hot tack strength, even under rigorousmanufacturing conditions. For some applications, there is also a needfor such materials to be repulpable.

SUMMARY

This disclosure is directed generally to various packaging materials,methods of making such packaging materials, and methods of using suchpackaging materials.

The packaging material may generally include a substrate, for example,paper, and a heat seal layer disposed on the substrate. The heat seallayer may comprise one or more polymers or polymeric materials that arecapable of forming a heat seal. In one example, the heat seal layer maycomprise polyvinylidene chloride (PVdC).

The packaging material may include (e.g., be provided with) at leastabout 8 wt % moisture (e.g., water), for example, from about 10 wt % toabout 18 wt % moisture. The moisture may be contained substantiallywithin the substrate, although it is contemplated that some moisture maybe disposed on or in the heat seal layer. The presence of at least about8 wt % moisture increases the hot tack of the seal (i.e., the tackinessor strength of a seal immediately after formation but beforesolidification of the sealing material), as compared with the hot tackof a seal formed from a similar packaging material with less than about8 wt % moisture. This increase in hot tack may be advantageous fornumerous packaging applications, and may be particularly advantageouswhere low temperature heat sealing is needed, for example, to increaseproduction rates. Additionally, the increase in hot tack may allow aheavier “charge” (i.e., product content) to be dropped into the bagwithout causing the seal to fail. Further, the presence of at leastabout 8 wt % moisture has been found to increase the hot tack window ofthe packaging material, thereby increasing the range of operatingconditions that may be used to successfully form a heat seal.

If desired, the packaging material containing the at least about 8 wt %moisture may be wound into a roll. The packaging material may be used inthe formation of various packages, wraps, pouches, or other constructsfor containing food items, seeds, or any other item prone to spoilage orleakage. The packaging material may also be repulpable.

Other features, aspects, and embodiments will be apparent from thefollowing description and the accompanying figures and examples.

BRIEF DESCRIPTION OF THE DRAWINGS

The description refers to the accompanying schematic drawings, in whichlike reference characters refer to like parts throughout the severalviews, and in which:

FIGS. 1-4 are schematic cross-sectional views of exemplary packagingmaterials; and

FIGS. 5-9 present the hot tack or heat seal strength data for exemplarypackaging materials at various moisture levels.

DESCRIPTION

Various aspects of the invention may be illustrated by referring to thefigures, which depict examples of packaging materials. For purposes ofsimplicity, like numerals may be used to describe like features. It willbe understood that the relative thicknesses of the various layers may bealtered or exaggerated for purposes of illustration, and that suchthicknesses are not indicative of actual or relative thicknesses ofactual structures.

FIG. 1 depicts a schematic cross-sectional view of an exemplarypackaging material 100. The packaging material 100 generally includes aplurality of layers in a substantially facing, contacting relationshipwith one another. The packaging material 100 may be formed into apackage using any suitable process, for example, a conventional form andfill type process.

In the exemplary embodiment shown in FIG. 1, the packaging material 100includes a substrate 102 and a heat seal layer 104 in a facingrelationship with one another. The packaging material also includes apair of outermost surfaces 106, 108 opposite one another, in thisexample, defined by the outermost surfaces of the heat seal layer 104and substrate 102, respectively. When the packaging material 100 isformed into a package, outermost surface 108 (in this example, theexposed surface of the substrate 102) generally faces outwardly fromand/or defines the exterior side or surface of the package, andoutermost surface 106 (in this example, the exposed surface of the heatseal layer 104) generally faces towards and/or defines the interior sideor surface of the package. The packaging material may include additionallayers, as will be discussed below.

The substrate 102 generally comprises a base material from which thepackaging material 100 is formed, for example, paper or paperboard.

The heat seal layer 104 generally comprises a polymer or polymericmaterial that is capable of being sealed against (i.e., bonded or joinedto) itself or another material in the presence of heat. In one exemplarypackaging material 100, the heat seal layer 104 may comprisepolyvinylidene chloride (PVdC). A PVdC heat seal layer 104 may alsoserve as a barrier layer for reducing the transmission of air, watervapor, and other gases through the packaging material 100. Examples ofPVdC that may be suitable for use with the packaging material 100include DARAN® SL112, DARAN® SL143, DARAN®SL158, and DARAN® SL159, eachof which is available commercially from Owensboro Specialty Polymers(Owensboro, Ky.). The heat seal and barrier properties of such materialsas provided by the manufacturer are set forth in Table 1. However, otherPVdC polymers and/or other polymers or polymeric materials may besuitable.

TABLE 1 OTR* WVTR* Heat seal (cc/100 sq. in./24 h) (g/100 sq. in./24 h)temp. lower 25° C., 65% RH 100° F., 90% RH DARAN ® limit 2.5 7.5 2.5 7.5product (° F.) lb/ream lb/ream lb/ream lb/ream SL112 270 0.34 0.13 0.490.15 SL143 250 1.40 0.43 1.10 0.34 SL158 230 0.96 0.32 0.53 0.18 SL159230 1.00 0.32 0.55 0.18

The packaging material 100 may generally include (e.g., be providedwith) at least about 8 wt % moisture (e.g., water), which may generallybe bound within (or disposed on) the paper substrate. For example, thepackaging material 100 may include from about 10 wt % to about 18 wt %moisture, for example, from about 12 wt % to about 16 wt % moisture. Inone particular example, the packaging material 100 may include about 14wt % moisture. However, other moisture levels and ranges thereof may besuitable.

Under typical manufacturing conditions, the moisture content of thepackaging material may be less than about 8 wt %, for example, fromabout 5 to about 7 wt %. However, the present inventors have discoveredthat a moisture content of at least about 8 wt % may significantlyincrease the hot tack of the packaging material, as compared with apackaging material containing less than about 8 wt % moisture. Forexample, in some instances, the hot tack of a packaging material with amoisture level of at least about 8 wt % may be about 25%, about 30%,about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about65%, about 70%, about 75%, about 80%, about 85%, about 90%, about 95%,about 100%, about 105%, about 110%, about 115%, about 120%, about 125%,about 130%, about 135%, about 140%, about 145%, about 150%, about 155%,about 160%, about 165%, about 170%, about 175%, about 180%, about 185%,about 190%, about 195%, or about 200% greater than a similar packagingmaterial with less than about 8 wt % moisture.

This result is unexpected and surprising. While not wishing to be boundby theory, it is believed that the additional moisture may make thesubstrate more pliable, which may then allow the heat seal layer of thepackaging material to make better contact with, and adhere to, itselfmore effectively. Alternatively or additionally, the additional moisturemay increase the heat transfer from the sealing device to the heal seallayer. In any case, unlike many presently available materials that creepor flow when the heat seal is stressed (e.g., when the contents areadded to the bag on a form and fill packaging machine), a heat sealformed using the present packaging material may remain intact using aheavier product charge (i.e., package contents), and may remain intactover a greater range of temperatures, thereby rendering the packagingmaterial more suitable for a wider range of commercial applications.

Additionally, the present inventors have discovered that the presence ofat least about 8 wt % moisture in the packaging material (e.g., withinthe substrate) has been found to increase the hot tack window of thepackaging material. As a result, the packaging material may be formedinto a package at a wider range of temperatures and/or other operatingconditions.

Further, the present inventors have generally observed that a lowerpolymer coat weight material with a relatively high moisture content canprovide a hot tack that is at least equivalent to the hot tack of apackaging material including a higher polymer coat weight material and arelatively low moisture content. Thus, the desired level of hot tack maybe achieved using less polymer. This may provide a significant costadvantage in many packaging applications.

Notably, the packaging material 100 is also repulpable and recyclablebecause the PVdC of the heat seal layer 104 can be readily dissociatedfrom the cellulose fibers of the paper substrate 102.

FIGS. 2-5 illustrate several exemplary variations of the packagingmaterial 100 of FIG. 1. The various packaging materials 200, 300, 400include features that are similar to the packaging material 100 shown inFIG. 1, except for variations noted and variations that will beunderstood by those of skill in the art. For simplicity, the referencenumerals of similar features are preceded in the figures with a “2”(FIG. 2), “3” (FIG. 3), or “4” (FIG. 4) instead of a “1”.

For example, in the exemplary packaging material 200 of FIG. 2, apolymer layer 210 (e.g., first polymer layer) is disposed between thesubstrate 202 and heat seal layer 204 (e.g., second polymer layer).Polymer layer 210 may comprise any suitable material and may be providedfor any purpose, as needed or desired for a particular packagingapplication.

In one example, both polymer layers 204, 210 may comprise PVdC. In suchan example, the layers 204, 210 may be configured to impart variousattributes to the resulting packaging material 200. For example, polymerlayer 204 may be selected based on its heat seal properties, whilepolymer layer 210 may be selected based on its hold out propertiesand/or barrier properties. As another example, both polymers 204, 210may be selected based on their heat seal properties. For instance, byselecting two PVdC polymers having different softening temperatures, therange of heat seal temperatures of the packaging material 200 may beeffectively broadened, which allows for a greater range of operatingconditions on the packaging equipment.

Thus, in one particular example, polymer layer 210 may compriseDARAN®SL112 and polymer layer 204 may comprise DARAN® SL158 and/orDARAN® SL159. In another example, polymer layer 210 may comprise DARAN®SL143 and polymer layer 204 may comprise DARAN® SL158 and/or DARAN®SL159. In still another example, polymer layer 210 may comprise DARAN®SL112 and polymer layer 204 may comprise DARAN® SL143.

Other examples of polymers that may be suitable for polymer layer 210include, but are not limited to, ethylene vinyl alcohol (EVOH), barrierfluoropolymer, other readily repulpable materials, or any combinationthereof. Further, one or primer layers may be used to obtain the desiredlevel of adhesion between the various layers of the packaging material.Numerous other possibilities are contemplated.

In addition to providing the desired heat seal and barriercharacteristics, the packaging material 200 may also be repulped andrecycled.

Turning now to FIG. 3, the packaging material 300 may also include oneor more coatings or layers that modify the surface characteristics ofthe packaging material. Such layers may generally comprise outermostlayers of the packaging material. For example, an anti-blocking layer orcoating 312 may be applied to polymer layer 304, as shown in FIG. 3. Inother embodiments, the polymer layer 304 may include an anti-blockingadditive or material (e.g., as with DARAN® SL159), so that no additionallayer 312 is necessary. Alternatively or additionally, a slip modifier314 (e.g., a wax) may be applied to the exposed side of the substrate302 to modify the coefficient of friction of the substrate 302. As withthe above materials, packaging material 300 may also be repulped andrecycled.

In another example shown in FIG. 4, the packaging material 400 includesa polymer layer 410 (which may be similar to polymer layer 210) disposedbetween the substrate 402 and heat seal layer 404, and a slip modifier414 (e.g., a wax) (which may be similar to slip modifier 314) disposedon the substrate 402. In such an example, the slip modifier 414 maydefine at least a portion of the outermost surface 408 of the packagingmaterial 400. As with the above materials, packaging material 400 mayalso be repulped and recycled.

While some exemplary packaging materials (e.g., packaging materials 100,200, 300, 400) are illustrated herein, it will be appreciated thatcountless other possibilities are contemplated. Each packaging materialand the layers thereof may vary for each application. Further, any ofthe various layers described above may be used in any combination, asneeded or desired for a particular packaging application. It also willbe appreciated that various materials may be used to form each layer ofthe packaging material, and that each layer may have various basisweights or coat weights, depending on the particular application.Further, layers may be added or omitted as needed or desired for eachpackaging application.

For example, the substrate (e.g., substrate 102, 202, 302, 402) may havea basis weight of from about 20 to about 330 lb/ream (lb/3000 sq ft.),for example, from about 40 to about 60 lb/ream, for example, from about25 to about 45 lb/ream. Other ranges and basis weights are contemplated.

The substrate may be flat or extensible. Further, if desired, thesubstrate may comprise a grease resistant material, for example, a paperor paperboard that is impregnated (or otherwise treated with) a greaseresistant chemical, for example, fluorochemical. Alternatively, thepaper or paperboard may be coated with one or more grease resistantmaterials.

Further, one or more portions or sides of the substrate may be coatedwith varnish, clay, or other materials, either alone or in combination.For example, at least the side of the substrate that will form anexterior surface of the package may be coated with a clay coating orother base coating. The coating may then be printed over with productadvertising, images, price coding, any other information or indicia, orany combination thereof. The base coating then may be overcoated with avarnish to protect any information printed thereon.

Each polymer layer (e.g., polymer layer 104, 204, 210, 304, 404, 410)independently may have a dry basis weight of from about 1 lb/ream toabout 10 lb/ream, for example, about 1 lb/ream, about 1.5 lb/ream, about2 lb/ream, about 2.5 lb/ream, about 3 lb/ream, about 3.5 lb/ream, about4 lb/ream, about 4.5 lb/ream, about 5 lb/ream, about 5.5 lb/ream, about6 lb/ream, about 6.5 lb/ream, about 7 lb/ream, about 7.5 lb/ream, about8 lb/ream, or any other suitable dry basis weight.

The combined dry basis weight of the polymer layers of the particularpackaging material may be less than about 20 lb/ream, for example, about15 lb/ream, about 14 lb/ream, about 13 lb/ream, about 12 lb/ream, about11 lb/ream, about 10 lb/ream, about 9 lb/ream, about 8 lb/ream, about 7lb/ream, about 6 lb/ream, about 5 lb/ream, about 4 lb/ream, or any othersuitable weight. In one specific example, the heat seal layer (e.g.,polymer layer 104, 204, 304, 404) may have a basis weight of from about4 to about 10 lb/ream, for example, about 7 lb/ream, and theintermediate polymer layer (e.g., polymer layer 210, 410) may have abasis weight of from about 2 to about 8 lb/ream, for example, about 5lb/ream. However, other basis weights and ranges are contemplatedhereby.

Where barrier properties are sought, any or all of the polymer layers(e.g., polymer layers 104, 204, 210, 304, 404, 410) may have an oxygentransmission rate (OTR) as measured using ASTM D3985 of less than about75 cc/m²/day, less than about 60 cc/m²/day, less than about 50cc/m²/day, less than about 45 cc/m²/day, less than about 30 cc/m²/day,less than about 20 cc/m²/day, less than about 10 cc/m²/day, less thanabout 1 cc/m²/day, or any other suitable OTR or range of OTRs. Likewise,in each of various independent examples, any or all of the polymerlayers e.g., polymer layers 104, 204, 210, 304, 404, 410) of theparticular packaging material may have a water vapor transmission rate(WVTR) as measured using ASTM F1249 of less than about 100 g/m²/day,less than about 50 g/m²/day, less than about 15 g/m²/day, less thanabout 1 g/m²/day, less than about 0.1 g/m²/day, less than about 0.05g/m²/day, or any other WVTR or range of WVTRs.

It will be noted that, in some applications, for example, French frybags, the package may include slits or other features to permit the airto escape after filling the package. This allows a plurality of packagesto be packed more efficiently into boxes or other cartons for shipping.In such applications, any measure of barrier properties would pertainonly to the areas of the material without such slits.

Where used, a slip modifying coating or layer (e.g., slip modifier 314,414) may have a coat weight (dry) of less than about 1 lb/ream, forexample, from about 0.05 to about 0.8 lb ream, for example, from about0.1 to about 0.6 lb/ream, for example, from about 0.25 to about 0.5lb/ream. Other ranges and amounts are contemplated.

The various layers of the packaging material (e.g., packaging material100, 200, 300, 400) may be formed, assembled, and/or joined in suitablemanner. In one exemplary process, the various layers (e.g., polymerlayers 104, 204, 210, 304, 404, 410) may be coated onto the substrate(e.g., substrate 102, 202, 302, 402) as aqueous dispersions and thendried. The moisture content of the packaging material may then beincreased to the desired level using any suitable process. For example,in one exemplary process, the packaging material may pass through aplurality of coaters or sprayers (or other treater) that apply water tothe substrate. The precise number of such coaters or sprayers may dependon the desired level of moisture in the packaging material. In someembodiments, one coater or sprayer may be sufficient, while in otherembodiments, two or more coaters or sprayers may be needed to attain thedesired moisture content. If desired, one or more of such coaters orsprayers also may be used to apply a slip modifier (e.g., slip modifier314, 414) to the substrate, either separately from or concurrently with(e.g., blended with) the water used to moisturize the packagingmaterial. Numerous other processes may be used.

After the water is applied to the substrate, the packaging material maybe supplied substantially directly to a conventional form and fillpackaging machine or any other suitable manufacturing machine to form apackage, or the packaging material (including the at least about 8 wt %moisture) may be formed into a roll that extends around a core, such asa tubular core, either for substantially immediate use or for later use.The packaging material (including the at least about 8 wt % moisture)may then be unwound from the roll and then be supplied to theconventional form and fill packaging machine or any other suitablemanufacturing machine. For example, the packaging material may be formedinto a tube (or tubular structure) with the heat seal layer facinginwardly, the edges may be joined to one another (e.g., to form a finseal), and the inwardly facing heat seal layer may be joined to itself(e.g., as opposed panels or faces of the tube, such that a first portionof the heat seal layer is sealed to a second portion of the heat seallayer) to form end seals. As stated above, the use of at least about 8wt % moisture in the present packaging material provides increased hottack and an increased hot tack window relative to similar packagingmaterials having a lower moisture content.

In accordance with one aspect of this disclosure, irrespective ofwhether the packaging material is supplied directly or indirectly (e.g.,by way of a roll) to the conventional form and fill packaging machine orany other suitable manufacturing machine, the seals (e.g., for forming apackage such as a bag) may be formed in the packaging material prior toany substantial drying of the packaging material. Accordingly, each ofthe above-discussed moisture contents may be applicable to the packagingmaterial immediately after the application of the water thereto, whilethe packaging material in roll form and/or the packaging material whilethe seals (e.g., for forming a package such as a bag) are formedtherein. Accordingly, provisions may be made that seek to inhibit anyundesirable drying of the packaging material. For example, if a roll ofpackaging material may not be used for an extended period of time and/ormay be exposed to an environment that may dry the packaging material toan undesired level, the roll of the packaging material may be wrapped ina protective material (e.g., polymer film), or the like. It is alsocontemplated that where undesirable moisture loss has occurred, thepackaging machine may be provided with a source of water (e.g., sprayer,roll coater, or other suitable apparatus) for increasing the moisturecontent of the packaging material prior to forming the packagingmaterial into a package.

The present invention may be understood further by way of the followingexamples, which are not to be construed as limiting in any manner. Allvalues are approximate unless otherwise noted.

Example 1

Various packaging materials were formed on production machinery andevaluated for hot tack at various moisture levels. First, 43 lb/reamnatural Kraft paper was coated with about 7 lb/ream of DARAN® SL112 PVdCand dried at a speed of 800 fpm at a temperature of about 300° F. Thecoated sheet was then coated with about 5 lb/ream of DARAN® SL159 PVdCand dried at a temperature of about 360° F. After drying, the packagingmaterials were moistened at 750 fpm using a Dahlgren moisturizer using amixture of 98.7 parts water and 1.3 parts Michemlube 156 (Michelman,Cincinnati, Ohio) applied to the underside of the sheet. The applicatorroll speed was varied to produce a range of moisture contents. Moisturewas measured on a Moistrex moisture analyzer.

The hot tack of the packaging materials was evaluated using ASTM 1921-98with a Lako Tools SL-10 Hot Tack and Seal Strength Tester (jaw pressureof 60 psi, seal time of 0.25 sec, and seal area of 0.75 square inches)over a temperature range of 210° F. to 310° F. at 20° F. intervals. Theresults are presented in Table 2 and FIG. 5.

TABLE 2 Seal Temp Hot tack at various moisture levels (g/in) (° F.) 6.8wt % 10.6 wt % 12.2 wt % 14.3 wt % 210 89 94 130 293 230 245 225 301 547250 300 413 489 741 270 298 542 673 773 290 409 658 725 784 310 468 663747 814

As is evident from FIG. 5 and Table 2, the hot tack of the packagingmaterials generally increased with moisture content and sealtemperature. It will be noted that while this effect has been describedherein with PVdC, it will be appreciated that increasing the moisturelevel of packaging materials including other heat seal layers also mayresult in an enhanced hot tack.

Example 2

Samples of the packaging material formed in Example 1 were evaluated todetermine whether the packaging material was repulpable. Despite thepresence of the PVdC layers, the polymers separated from the fiber inwater and were retained on a 0.010″ flat screen so that the fibers couldbe successfully be reformed into paper. This may provide a significantadvantage over other packaging materials that are not repulpable.

Example 3

The hot tack temperature window (i.e., the range between the lower andupper self-tack limits) was determined for the material of Example 1 atvarious moisture levels using a Sencorp Heat Sealer, Model 12ASL/1,fitted with a Hot Tack Attachment with a 200 g weight. A 2 by 4 inchsample was placed into the apparatus and pushed into sealing jaws withthe weight supported by hand. The seal conditions were 80 psi and 0.25sec. As the jaws closed, the weight was released and the sample wasremoved from the jaws. The width of the seal that was pulled apart bythe falling action of the weight was recorded. The material passed thetest if less than 0.25 inch of the sealed area separated. The highestand lowest temperature at which the material passed the test defines thehot tack window. The results are presented in Table 3. As indicated inTable 3, the samples including 14.2 wt % moisture had a wider hot tackwindow than the samples including 9.5 wt %.

TABLE 3 Moisture level Low hot tack High hot tack Hot tack window (wt %)(° F.) (° F.) (° F.) 9.5 270 385 115 14.2 240 400 160

Example 4

Various packaging materials were evaluated for hot tack and heat sealstrength. To form the base packaging material, a 43 lb/ream TEA-Kraftpaper (Spec 2400 from Longview Fibre Paper and Packaging, Inc., LongviewWash.) was coated with about 6-7 lb/ream DARAN® SL112 PVdC and dried.The material was then coated with about 5-6 lb/ream DARAN® SL159 PVdCand dried. The total polymer weight was about 12 lb/ream.

To form the experimental packaging materials (i.e., the packagingmaterials with a moisture level above about 8 wt %), the coated paperwas then moisturized with water using a Dahlgren moisturizer. Themoisturized packaging material was then perforated and again moisturized(on the paper side) with a mixture of 98.7 parts water and 1.3 partsMichemlube 156.

The resulting packaging materials were evaluated for hot tack and heatseal strength as described in Example 1. Moisture was measured on aMoistrex moisture analyzer. The results are presented in Tables 4-5 andFIGS. 6-7, where % A is the percent improvement in hot tack as measuredusing the average hot tack of the control materials (<8 wt % moisture)and the average of the experimental materials (about 15 wt % moisture).

TABLE 4 Hot tack at various moisture levels (g/in) Seal Moisture, Tempcontrol matls (wt %) Moisture, expt matls (wt %) (° F.) 5.3 6.1 7.2 AVG14.6 14.9 15.7 AVG % Δ 210 248 206 128 194 436 608 570 538 177 230 273332 273 293 708 529 535 591 102 250 383 508 377 423 834 670 712 739 75270 560 645 437 547 834 745 685 755 38 290 484 610 485 526 853 790 678774 47 310 499 616 621 579 927 731 779 812 40

TABLE 5 Heat seal strength at various moisture levels (g/in) SealMoisture, experimental Temp Moisture, control matls (wt %) matls (wt %)(° F.) 5.3 6.1 7.2 14.6 14.9 15.7 210 10 10 36 13 9.0 35 230 28 35 0 25449 351 250 396 554 219 498 579 640 270 688 673 807 858 605 688 290 718721 1027 1000 676 675 310 806 717 1110 1034 730 735

All of the experimental materials exhibited improved hot tack at theelevated moisture levels, with the most significant increases beingobserved at the lower heat seal temperatures. The increase in hot tackat lower temperatures may be particularly advantageous where lower heatseal temperatures are needed to achieve higher production rates.

Example 5

Various packaging materials were evaluated for hot tack and heat sealstrength. To form the base packaging material, a 43 lb/ream TEA-Kraftpaper (Spec 2400 from Longview Fibre Paper and Packaging, Inc., LongviewWash.) was coated with about 8 lb/ream DARAN® SL112 PVdC, and dried. Theresulting material was then coated with about 6 lb/ream DARAN® SL159PVdC and dried. The total polymer weight was about 14 lb/ream.

The coated paper was then moisturized with water using a Dahlgrenmoisturizer, perforated, and again moisturized (on the paper side) witha mixture of 98.7 parts water and 1.3 parts Michemlube 156.

The resulting packaging materials were evaluated for hot tack and heatseal strength as described in Example 1. Moisture was measured on aMoistrex moisture analyzer. The results are presented in Table 6 andFIG. 8.

TABLE 6 Heat seal Seal Temp Hot tack (g/in) strength (g/in) (° F.) 8.6wt % moisture 13 wt % moisture 13 wt % moisture 210 427 687 35 230 532816 75 250 614 940 704 270 649 952 1024 290 616 967 1127 310 658 10291123

Example 6

Various packaging materials were evaluated for hot tack and heat sealstrength. To form the base packaging material, a 43 lb/ream TEA-Kraftpaper (Spec 2400 from Longview Fibre Paper and Packaging, Inc., LongviewWash.) was coated with about 4-5 lb/ream DARAN® SL112 PVdC, dried,coated with about 3-4 lb/ream DARAN® SL159 PVdC, and dried. The totalpolymer weight was about 8 lb/ream.

The coated paper was then moisturized using a Dahlgren moisturizer. Themoisturized packaging material was then perforated and again moisturized(on the paper side) with a mixture of 98.7 parts water and 1.3 partsMichemlube 156 (Michelman). The resulting packaging materials wereevaluated for hot tack and heat seal strength as described in Example 2.Moisture was measured on a Moistrex moisture analyzer. The results arepresented in Table 7 and FIG. 9.

TABLE 7 Seal Hot tack (g/in) at various Heat seal strength (g/in) atvarious Temp moisture levels moisture levels (° F.) 8.3 wt % 8.6 wt % 13wt % 14.4 wt % 8.3 wt % 8.6 wt % 13 wt % 14.4 wt % 210 49 118 149 30 1514 0 16 230 198 267 389 527 80 43 53 84 250 280 448 577 598 542 549 552527 270 527 526 660 661 741 683 729 675 290 635 724 729 759 830 730 741733 310 632 706 739 686 802 727 774 742

Viewing Examples 4-6, it can generally be observed that for a givenpackaging material, the hot tack increases with moisture content. Thus,the presence of at least about 8 wt % moisture in the packaging materialmay allow the packaging material to be used under more rigorousconditions. For example, a packaging material according to the presentdisclosure may be used to form a package with heavier product contents,since the seal is able to withstand the heavier load being dropped intothe package. This may provide a significant advantage for many packagingapplications.

Further, it can also be generally observed that at a given moisturelevel (or average moisture level), as the total polymer coat weight isincreased, the hot tack increases. Stated differently, a lower polymercoat weight material with a high moisture content can provide at leastequivalent (and in some cases, increased) hot tack to a higher polymercoat weight material with a lower moisture content. As a result, it maybe possible to achieve the same (or better) level of hot tack using lesspolymer. This may provide a significant cost advantage over previouslyavailable packaging materials.

Although certain embodiments of this invention have been described witha certain degree of particularity, those skilled in the art could makenumerous alterations to the disclosed embodiments without departing fromthe spirit or scope of this invention. All directional references (e.g.,over, under, inner, outer, upper, lower, upward, downward, left, right,leftward, rightward, top, bottom, above, below, vertical, horizontal,clockwise, and counterclockwise) are used only for identificationpurposes to aid the reader's understanding of the various embodiments ofthe present invention, and do not create limitations, particularly as tothe position, orientation, or use of the invention unless specificallyset forth in the claims. Joinder references (e.g., joined, attached,coupled, connected, and the like) are to be construed broadly and mayinclude intermediate members between a connection of elements andrelative movement between elements. As such, joinder references do notnecessarily imply that two elements are connected directly and in fixedrelation to each other. Further, all percentages herein are weightpercentages, unless specified otherwise.

It will be recognized by those skilled in the art, that various elementsdiscussed with reference to the various embodiments may be interchangedto create entirely new embodiments coming within the scope of thepresent invention. It is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative only and not limiting. Changes in detail or structuremay be made without departing from the spirit of the invention. Thedetailed description set forth herein is not intended nor is to beconstrued to limit the present invention or otherwise to exclude anysuch other embodiments, adaptations, variations, modifications, andequivalent arrangements of the present invention.

Accordingly, it will be readily understood by those persons skilled inthe art that, in view of the above detailed description of theinvention, the present invention is susceptible of broad utility andapplication. Many adaptations of the present invention other than thoseherein described, as well as many variations, modifications, andequivalent arrangements will be apparent from or reasonably suggested bythe present invention and the above detailed description thereof,without departing from the substance or scope of the present invention.

While the present invention is described herein in detail in relation tospecific aspects, it is to be understood that this detailed descriptionis only illustrative and exemplary of the present invention and is mademerely for purposes of providing a full and enabling disclosure of thepresent invention and to provide the best mode contemplated by theinventor or inventors of carrying out the invention. The detaileddescription set forth herein is not intended nor is to be construed tolimit the present invention or otherwise to exclude any such otherembodiments, adaptations, variations, modifications, and equivalentarrangements of the present invention.

1. A packaging material, comprising: a substrate, the substratecomprising paper; and a heat seal layer disposed on the substrate, theheat seal layer comprising polyvinylidene chloride, wherein thepackaging material includes at least about 8 wt % moisture.
 2. Thepackaging material of claim 1, wherein the packaging material includesfrom about 10 wt % to about 18 wt % moisture.
 3. The packaging materialof claim 1, wherein the packaging material includes from about 12 wt %to about 16 wt % moisture.
 4. The packaging material of claim 1, whereinthe packaging material includes about 14 wt % moisture.
 5. The packagingmaterial of claim 1, wherein the moisture is substantially containedwithin the substrate.
 6. The packaging material of claim 1, wherein thepackaging material is wound into a roll.
 7. The packaging material ofclaim 1, wherein the moisture is for increasing the hot tack of a sealformed between a first portion of the heat seal layer and a secondportion of the heat seal layer relative to a seal formed using apackaging material with less than about 8 wt % moisture.
 8. Thepackaging material of claim 7, wherein the hot tack of the packagingmaterial is at least about 25% greater than the hot tack of thepackaging material with less than about 8 wt % moisture.
 9. Thepackaging material of claim 7, wherein the hot tack of the packagingmaterial is at least about 40% greater than the hot tack of thepackaging material with less than about 8 wt % moisture.
 10. Thepackaging material of claim 7, wherein the hot tack of the packagingmaterial is at least about 75% greater than the hot tack of thepackaging material with less than about 8 wt % moisture.
 11. Thepackaging material of claim 7, wherein the hot tack of the packagingmaterial is at least about 100% greater than the hot tack of thepackaging material with less than about 8 wt % moisture.
 12. Thepackaging material of claim 1, further comprising a polymer layerdisposed between the substrate and the heat seal layer.
 13. Thepackaging material of claim 12, wherein the polymer layer comprises atleast one of polyvinylidene chloride, ethylene vinyl alcohol, andbarrier fluoropolymer.
 14. The packaging material of claim 1, furthercomprising a slip modifier disposed on a side of the substrate oppositethe heat seal layer.
 15. The packaging material of claim 1, wherein theheat seal layer further comprises an anti-blocking material.
 16. Thepackaging material of claim 1, wherein the substrate further comprises agrease resistant material.
 17. The packaging material of claim 16,wherein the grease resistant material comprises a fluorochemical. 18.The packaging material of claim 1, wherein the packaging material isrepulpable.
 19. A packaging material, comprising: a substrate, thesubstrate comprising paper; a first polymer layer disposed on thesubstrate, the first polymer layer comprising polyvinylidene chloride;and a second polymer layer disposed on the first polymer layer, thesecond polymer layer comprising polyvinylidene chloride, the secondpolymer layer comprising an outermost surface of the packaging material,wherein the packaging material includes at least about 8 wt % moisture.20. The packaging material of claim 19, wherein the hot tack of a sealformed between a first portion of the heat seal layer and a secondportion of the heat seal layer is at least about 25% greater than thehot tack of a heat seal formed using a packaging material with less thanabout 8 wt % moisture.
 21. A method of forming a package, the methodcomprising: forming a packaging material into a tubular structure, thepackaging material comprising a substrate, the substrate comprisingpaper, and a heat seal layer disposed on the substrate, the heat seallayer comprising polyvinylidene chloride, the packaging materialincluding at least about 8 wt % moisture, wherein the tubular structurehas a pair of opposed inner surfaces, each surface comprising the heatseal layer of the packaging material; and bringing the inner surfacesinto contact with one another in the presence of heat to form a seal.22. The method of claim 21, wherein the hot tack of the seal is at leastabout 25% greater than a packaging material with less than about 8 wt %moisture.